The first interesting detail is the SteamVR Performance Test files cites specific Source 2 directories: "left4dead3" and "hl3". That's not much itself, but breaking down the code within these files uncovers references to a possible Half-Life 3 quest system. Half-Life 3 having a quest system isn't a new rumor, but these strings do add to the body of evidence that NPCs can provide quests to Gordon Freeman during the game. Also bundled into these files? Strings detailing a "crowbar zipline" and a grenade launcher armed with "weapon_spygrenade".

Left 4 Dead 3 files weren't absent from the investigation either. Along with references to a Source 2 day-night cycle, there are hints of a new zombie type called "the nocturnal". Presumably if Left 4 Dead 3 introduces a day-night cycle, this would be a special infected enemy which only spawns once the sun goes down.

The SteamVR demo also contains texture files for two new Half-Life 3 and Left 4 Dead 3 characters, although their exact roles in the games - if any - isn't clear. On top of that, the demo seems to contain unusable Source 2 development maps referencing Aperture Science and possible space flight mechanics. That latter map is probably a reference Valve's cancelled space pirate game Stars of Blood, but at this point, it's nice to image Half-Life 3 literally shooting for the stars.

As always, nothing here is official confirmation from Valve, or in any way reflects finished Half-Life 3 or Left 4 Dead 3 products - assuming they're coming at all. All the same, wouldn't it be great to get excited for a new Valve software product that wasn't Dota 2 updates or Team Fortress 2 hats? Here's hoping at least some of this info makes its way into finished games.